This thread sums things up nicely:

http://ez.no/community/forum/setup_design/sos_paypal_checkamount_failed_solved/re_sos_paypal_checkamount_failed_solved

I came across the same issue today, and noticed there was no bug report for what in reality is a mind numbingly easy bug to fix, and yet has horrible and unpleasant consequences when your realise your customer orders are disappearing into the ether.

Steps to reproduce

• Make a shopping cart using ez and ezpaypal
• Buy stuff a few times
• Stare aghast as your lovely cash is siphoned off by paypal and leaves not a trace in the webshop!
• Boggle at error messages like "checkAmount failed: Order amount (7.61) and received amount (7.61) do not match" in eZPaypalChecker.log!